Reverse thermal gels as support for rapid prototyping

ABSTRACT

The present invention relates to novel polymeric compositions that exhibit Reverse Thermal Gelation (RTG) properties for use as Support Materials (SM) in the manufacture of three-dimensional objects. These polymers are Temperature Sensitive Polymers that respond with a significant change of properties to a small change in temperature. Temperature Sensitive Polymers exhibit cloud point (CP) or lower critical solution temperature (LCST) in aqueous solutions. Water-soluble Temperature Sensitive Polymers are chosen to give low viscosity liquid at low temperature when dissolved in water and by that to permit easy dispensing at low temperature. Raising the temperature above their gelation temperature (T gel ) will result in solidification of the composition. At its gel position the material has favorable characteristics as a support and building material. The gel layers have the appropriate toughness and dimensional stability to support the model layers during the building process. After the building process is completed the gel can be cooled down to a temperature below its T gel  so the gel can liquefy and be removed easily by rinsing with water.

RELATED APPLICATIONS

[0001] This application claims priority from provisional applicationU.S. Serial No. 60/312,490, filed Aug. 16, 2001, entitled “REVERSETHERMAL GELS AS SUPPORT FOR RAPID PROTOTYPING” which is incorporated inits entirety by reference herein.

FIELD OF THE INVENTION

[0002] Embodiments of the present invention relate to methods of usingnovel polymeric compositions as support and build materials for RapidPrototyping (RP), Rapid Manufacturing (RM) and Rapid Tooling (RT)processes. These polymeric compositions exhibit Reverse Thermal Gelation(RTG) properties, i.e. low viscosity at low temperature and highviscosity (or semi-solid) gels at higher temperatures.

BACKGROUND OF THE INVENTION

[0003] Rapid prototyping is a generic name of various technologies forproducing three-dimensional models, usually from three-dimensional CAD(Computer Aided Design) data.

[0004] One such technology is known in the art as three-dimensionalprinting, in which layers descriptive of the model are produced from theCAD data, then a curable liquid material, usually a photopolymer, isdispensed and cured layer by layer by exposure to light.

[0005] One such technique is disclosed in U.S. application Ser. No.,09/412,618 assigned to the applicants of the present invention, filedOct. 6, 1999, entitled “SYSTEM AND METHOD FOR THREE DIMENSIONAL MODELPRINTING,” incorporated herein by reference.

[0006] According to certain embodiments described in Ser. No.09/412,618, the model is produced from a building material (BM), whichis a curable liquid photopolymer, dispensed by ink jet multi-nozzlebeads. Simultaneously with the BM dispensing, a second set of ink jetheads dispenses Support Material (SM), which exhibit differentproperties from those of the BM.

[0007] Preferably, the SM is dispensed in locations where BM is absent,thus holding the liquid BM in place until being cured. At the conclusionof the model production, the SM is to be disposed without spoiling themodel.

[0008] There are many techniques, known in the art, for SM removal,which depend on the material properties. Using wax, for instance, as SM,enables SM removing by raising the model temperature beyond the meltingpoint of the SM.

[0009] Another known technique is stereolithography, in which use ismade of a single curable material in a container, curing selectivelyonly those portions required to form the model, the uncured portions areused as support materials and are removed at a later stage. Thistechnique is disclosed by for example U.S. Pat. No. 5,779,967 to Hull.

[0010] Rapid prototyping (RP) techniques are known in the art astechniques used to produce models out of three-dimensional CAD data. Inthe same way, rapid tooling (RT) manufacturing techniques are generallyused for rapid manufacturing of casting molds. Rapid manufacturing (RM)techniques are generally used for direct manufacturing of finishedparts.

[0011] In all of these prior art techniques the unnecessary part (i.e.the support, the mold or the core) should be disposed, leaving the otherpart intact. In these above-mentioned techniques, the materials used asSM do not exhibit the optimal combination of properties required, i.e.easy dispensing, toughness as supporting material, easy removal from thefinished model and friendliness to the environment. Thus, there is astrong need in the art for new and better materials that can be used tosupport 3-dimensional objects during construction.

SUMMARY OF THE INVENTION

[0012] In one embodiment, the present invention provides a compositionsuitable for supporting and/or building a three-dimensional object, thecomposition comprising at least one Temperature Sensitive Polymer, andat least one surface- active agent, wherein the composition exhibitsReverse Thermal (elation (RTG) properties.

[0013] Furthermore, in another embodiment, the present inventionprovides a method for building a three-dimensional object by threedimensional printing, the method comprising the steps of dispensing abuilding composition, comprising at least one Temperature SensitivePolymer, wherein the building composition exhibits Reverse ThermalGelation (RTG) properties and at least one surface-active agent; andgelating the building composition by increasing temperature to abovegelation temperature, thereby constructing the three dimensional object.

[0014] Furthermore, in another embodiment, the present inventionprovides a method for supporting a three-dimensional object duringconstruction, the method comprising the step of contacting the objectwith a support composition, comprising at least one TemperatureSensitive Polymer, wherein the support composition exhibits ReverseThermal Gelation (RTG) properties and, at least one surface-activeagent; gelating the support composition by increasing temperature toabove gelation temperature, thereby supporting the three dimensionalobject.

[0015] Furthermore, in another embodiment, the method farther comprisesthe step of easy removing the support composition after construction ofthe object by cooling the support composition to a temperature below thegelation temperature

[0016] Furthermore, in another embodiment, the construction comprisesRapid Prototyping (RP), Rapid Manufacturing (RM) or Rapid Tooling (RT).

[0017] In one embodiment, the construction comprises rapid tooling (RT),wherein the rapid tooling (RT) comprises building a casting mold withthe support composition for holding the object, and building the objectin the mold. In another embodiment, the method further comprises thestep of easy removing the mold by cooling the support composition to atemperature below the gelation temperature.

[0018] In another embodiment the construction comprises RapidManufacturing (RM), wherein the rapid manufacturing (RM) comprisesdirect manufacturing of finished parts.

[0019] In one embodiment, the Temperature Sensitive Polymer is awater-soluble Temperature Sensitive Polymer. In another embodiment, thewater-soluble Temperature Sensitive Polymer is an ABA triblock oligomer,wherein A and B are oligomers. In another embodiment, A is a hydrophilicoligomer and B is a hydrophobic oligomer, In another embodiment, A is ahydrophobic oligomer and B is a hydrophilic oligomer. In anotherembodiment, A and B comprise aliphatic polyether and/or polyester units.In another embodiment, A is poly(ethylene oxide) and B is poly(propyleneoxide).

[0020] In another embodiment, the water-soluble Temperature SensitivePolymer is a multi blocks polymer of (ABA-X)_(m), organized at random orrepetitive configuration, wherein wherein A and B are oligomers, m is aninteger of 1-30, and X is a chain extender. In one embodiment, X isselected from the group consisting of di, tri and poly isocyanates, di,tri and poly carboxylic acids, diacyl halides, triphosgene or anycombination thereof In another embodiment, A is a hydrophilic oligonmerand B is a hydrophobic oligomer. In another embodiment, A is ahydrophobic oligomer and B is a hydrophilic oligomer. In anotherembodiment the multi block polymer of ABA is a polyurethane, apolycarbonate, a polyester or any combination thereof.

[0021] In another embodiment, the Temperature Sensitive Polymer is apoly (N-substituted (meth)acrylamide), In one embodiment, the poly(N-substituted (meth)acrylamide) is a poly (N-isopropyl(meth)acrylamides). In another embodiment, the Temperature SensitivePolymer is a poly vinyl alcohol derivative, hydroxypropylmethylcellulose, ethyl hydroxyethyl cellulose (EHEC) or any combinationthereof.

[0022] In one embodiment, the surface-active agent is capable ofreducing the surface tension of the support and/or building compositionto about 30 dyne/cm. In another embodiment, the surface-active agent isa silicon surface-active agent additive, fluoro-based surface-activeagent or any combination thereof

[0023] Furthermore, in another embodiment, the support and/or buildingcomposition further comprise at least one photo curable reactivecomponent, at least one photo- initiator, and at least one stabilizer.In one embodiment, the method further comprises the step of curing thesupport and/or building composition, thereby increasing the strength ofthe support and/or building composition. In one embodiment, the curablereactive component is a (meth)acrylic component. In another embodiment,the (meth)acrylic component is a (.meth)acrylic monomer, a (meth)acrylicoligomer, or a combination thereof. In another embodiment, the(meth)acrylic component is a polyethylene glycol mono or di(meth)acrylated, polyether triacrylate or any combination thereof. Inanother embodiment, the reactive component is a water miscible componentthat is, after irradiation or curing, capable of dissolving or swellingupon exposure to water or to an alkaline or acidic water solution. Inanother embodiment, the water miscible component is an acryloylmorpholine, (meth)acrylated urethane oligomer derivative of polyethyleneglycol, a partially (meth)acrylated polyol oligomer, an (meth)acrylatedoligomer having hydrophillic substituents or any combination thereof Inanother embodiment, the hydrophilic substituents are acidicsubstituents, amino substituents, hydroxy substituents or anycombination thereof In another embodiment, the (meth)acrylic componentis beta-carboxyethyl acrylate. In one embodiment, the reactive componentis a molecule having one or more vinyl ether substituents. In anotherembodiment, the vinyl ether substituent is hydroxy-butyl vinyl ether.

[0024] In one embodiment, the photo-initiator is a free radicalphoto-initiator, a cationic photo-initiator, or any combination thereofIn one embodiment the free radical photo- initiators are benzophenonies,acylphosphine oxide, alpha-amino ketone TO any combination thereof Inone embodiment, the cationic photo-initiator is selected from the groupcomprising: aryldiazonium salts, diaryliodonium salts, triarylsulphoniumsalts, triarylselenonium salts and triarylsolfonium hexafluoroantimonatesalts, or any combination thereof.

[0025] In one embodiment, the photo-initiator further comprises aco-initiator component. In another embodiment, the co-initiatorcomponent is triethanol amine.

[0026] In one embodiment, the stabilizer is 4-inethoxy phenol.

[0027] Furthermore, in another embodiment, the present inventionprovides a method for the preparation of a three-dimensional object bythree-dimensional printing comprising the step of dispensing a modelcomposition from a first dispenser, the model composition comprising atleast one reactive component, at least one photo-initiator, at least onesurface-active agent, and at least one stabilizer; dispensing a supportcomposition from a second dispenser, the support composition comprisingat least one Temperature Sensitive Polymer, at least one surface-activeagent; and combining the model composition and the support compositionin pre-determined proportions to produce a multiplicity of constructionlayers for forming the three-dimensional object, whereby the modelcomposition is cured resulting in a solid form, and whereby the supportcomposition is gelated by increasing temperature to above gelationtemperature resulting in a gel form.

[0028] In one embodiment, the reactive component of the modelcomposition is selected from the group consisting of an acryliccomponent, a molecule having one or more epoxy substituents, a moleculehaving one or more vinyl ether substituents, vinylpyrolidone,vinylcaprolactam, or any combination thereof. In another embodiment, thereactive component of the model composition is comprised of at least oneacrylic component. In another embodiment, the acrylic component is anacrylic monomer, an acrylic oligonmer, an acrylic crosslinker, or anycombination thereof. In another embodiment, the reactive component ofthe model composition further comprises a molecule having one or moreepoxy substituents, a molecule having one or more vinyl ethersubstituents, vinylcaprolactam, vinylpyrolidone, or any combinationthereof, In another embodiment the reactive component of the modelcomposition further comprises vinylcaprolactam. In another embodimentthe reactive component of the model composition is a molecule having oneor more vinyl ether substituents. In another embodiment, the reactivecomponent of the model composition is a molecule having one or moreepoxy substituents.

[0029] In one embodiment, the photo-initiator of the model compositionis a free radical photo-initiator, a cationic photo-initiator or anycombination thereof.

[0030] In one embodiment, the model composition further comprises atleast one pigment and at least one dispersant In another embodiment, thepigment is a white pigment, an organic pigment, an inorganic pigment, ametal pigment or a combination thereof In another embodiment, the modelcomposition further comprises a dye.

[0031] Furthermore, in another embodiment, the present inventionprovides a three dimensional object, obtained by any of the methods ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will be understood andappreciated more fully from the following detailed description taken inconjunction with the appended drawings in which:

[0033]FIG. 1: A typical RTG graph of viscosity—temperature relation isshown. At a specific temperature T=T_(min) the specific composition hasits minimal viscosity Vmin. Raising the temperature causes the viscosityto increase until at T=T_(gel) the composition is transformed into geli.e. an abrupt change in its mechanical properties. Raising thetemperature further to T=T₂ will raise the viscosity until the requiredviscosity for supporting material is attained.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Embodiments of the present invention relate to novel polymericcompositions that exhibit Reverse Thermal Gelation (RTG) properties foruse as Support Materials (SM) in the manufacturer of three-dimensionalobjects. These polymers are Temperature Sensitive Polymers that respondwith a significant change of properties to a small change intemperature. Temperature Sensitive Polymers exhibit cloud point (CP) orlower critical solution temperature (LCST) in aqueous solutions.Water-soluble Temperature Sensitive Polymers are chosen to give lowviscosity liquid at low temperature when dissolved in water and by thatto permit easy dispensing at low temperature. Raising the temperatureabove their gelation temperature (T_(gel)) will result in solidificationof the composition. At its gel position the material has favorablecharacteristics as a support and building material. The gel layers havethe appropriate toughness and dimensional stability to support the modellayers during the building process. After the building process iscompleted the gel can be cooled down to a temperature below its T_(gel)so the gel can liquefy and be removed easily by rinsing with water.

[0035] In one embodiment, the methods of the present invention are usedwith systems and methods as described by the U.S. application of Ser.No. 09/412,618. In another embodiment the methods of the presentinvention may be used with other systems and methods for buildingthree-dimensional objects, for example, without limitation, forstereolithography, described above.

[0036] In one embodiment, the present invention provides a compositionsuitable for supporting and/or building a three-dimensional object, thecomposition comprising at least one Temperature Sensitive Polymer, andat least one surface-active agent, wherein the composition exhibitsReverse Thermal Gelation (RTG) properties. In another embodiment, thepresent invention further provides a method for building athree-dimensional object by three dimensional printing, the methodcomprising the steps of dispensing a building composition, comprising atleast one Temperature Sensitive Polymer, wherein the buildingcomposition exhibits Reverse Thermal Gelation (RTG) properties and atleast one surface-active agent; and gelating the building composition byincreasing temperature to above gelation temperature, therebyconstructing the three dimensional object. In another embodiment thepresent invention further provides a method for supporting athree-dimensional object during construction, the method comprising thestep of contacting the object with a support composition, comprising atleast one Temperature Sensitive Polymer, wherein the support compositionexhibits Reverse Thermal Gelation (RTG) properties and at least onesurface-active agent; gelating the support composition by increasingtemperature to above gelation temperature, thereby supporting the threedimensional object. In another embodiment, the present invention furtherprovides a method for the preparation of a three-dimensional object bythree-dimensional printing comprising the step of dispensing a modelcomposition from a first dispenser, the model composition comprising atleast one reactive component, at least one photo-initiator, at least onesurface-active agent, and at least one stabilizer; dispensing a supportcomposition from a second dispenser, the support composition comprisingat least one Temperature Sensitive Polymer, at least one surface-activeagent; and combining the model composition and the support compositionin pre-determined proportions to produce a multiplicity of constructionlayers for forming the three-dimensional object, whereby the modelcomposition is cured resulting in a solid form, and whereby the supportcomposition is gelated by increasing temperature to above gelationtemperature resulting in a gel form.

[0037] Non-limiting examples of polymeric compositions used withembodiments of the present invention are based on water solutions ofTemperature Sensitive Polymers, which exhibit RTG, for example.

[0038] 1. ABA triblocks oligomers.

[0039] 2. Multi blocks polymers of ABA, of random or repetitiveconfiguration.

[0040] 3. Star configuration molecules, often called radial.

[0041] 4. Grafted chains, often called comb.

[0042] The RTG phenomenon can be used to benefit:

[0043] 1. Easy dispensing at low temperature and low viscosity.

[0044] 2. The use of the dispensed material as a support material (SM)in the Rapid Prototyping (RP), Rapid Manufacturing (RM), and RapidTooling (RT) processes: raising the material temperature above itsgelation temperature will transform it into gel.

[0045] 3. Easy cleaning of the SM and BM: the RTG phenomenone isreversible, i.e. at a temperature lower than its gelation temperaturethe material liquefies, thus the SM can easily be washed off.

[0046] The effect of temperature is interesting: an increase in theaggregation number with increasing temperature has been observed, whilethe micellar radius remains constant. The conclusions are complicated bythe rather broad CMT transition, and the fact that dynamic lightscattering detects the micelle hydrodynamic radius, which includes thewater hydrating the EO segments,

[0047] PEO-PPO-PEO copolymer solutions of high copolymer concentrationexhibit a dramatic change in viscosity at temperatures close to ambient,revealing Reverse Thermal Gelation (RTG) properties. Many studies haveshown that the observed changes in viscosity are due to a “hard-spherecrystallization” as the micelle concentration approaches the criticalvolume fraction of 0.53 (micelles close-packed).

[0048] The RTG phenomenon is not constricted only to micellar polymericsystems, Another RTG property of the particular type of polymers-Ethyl(hydroxyethyl)cellulose (EHEC), was discovered some years ago byAndres Carlsson and his colleagues, Solutions of EHEC and ionicsurfactants of certain compositions are converted to gels when thetemperature is increase& Moreover, the anomalous behavior of theseEHEC-surfactant formulations is fully reversible as liquid solutionsform clear and stable gels but re-liquefy when cooled to temperaturesbelow the gelation point The transition can occur at temperatures as lowas 30-40° C. and the concentration of polymer and ionic surfactantneeded to bring about the thermal gelation is rather low-in total about1 wt %. The enhancement of surfactant binding to the EHEC polymericchains at increased temperatures has been proposed to play a major rolefor the gelation. At increasing temperature the surfactant aggregationnumbers becomes lower and the degree of ionization of the clustersbecomes higher. This is due to hydrophobic association of polymerhydrophobic parts with the clusters at higher temperature. Thus, as longas segments from more than one polymer chains are associated with theclusters, an increase in the number of clusters may lead to an increasedcross-linking which could result in gel formation.

[0049] Another type of temperature sensitive polymer is thePoly(N-isopropylacrylarnide) [Poly (NIPAM)]. This polymer when preparedusing free-radical initiators is soluble in solvents, which are capableof forming reasonably strong hydrogen bonds. In aqueous solution, itshows a lower critical solution temperature (LCST) at about 31° C. Poly(NIPAM) gel in water undergoes a volume-phase transition from swollengel to a shrunken gel at about 33.6 ° C. This is due to the hydrophobicinteraction between the polymer and water molecule. The phase separationtakes place by association of the polymer molecules into largeraggregates formed by intermolecular hydrogen bonding and nonpolar bonds.The tendency for the formation of such bonds is also enhanced by thedestabilization of ice like structure in water when nonpolar solutesaggregate. Alternatively, it is also possible to ascribe this phenomenonto the fact that the polymer is more ordered in dilute solution than inthe concentrated phase and that this ordering is due to the relativelystrong hydrogen bonds formed between water and the polymer. As thetemperature is raised, these hydrogen bonds become weaker and thesolution becomes unstable.

[0050] Embodiments of the present invention farther relate to methods ofusing these compositions in Rapid Prototyping (RP), Rapid Manufacturing(RM) and Rapid Tooling (RT). Accordingly, it is one object of anembodiment of the present invention to provide novel temperaturesensitive compositions in which can be used in the manufacturing of athree-dimensional object by three-dimensional printing.

[0051] It has now been discovered that these and other objectives can beachieved by the present invention, which provides polymeric compositionssuitable for supporting and/or building a three-dimensional object.

[0052] In one embodiment the support and/or building composition is usedas a support composition for supporting a three-dimensional objectduring construction. In another embodiment a model composition is usedas a building composition for the construction of a three-dimensionalobject.

[0053] In another embodiment the support and/or building composition isused as a building composition, for example, without limitation, inmedical applications.

[0054] Support and/or Building Composition

[0055] In one embodiment, the present invention provides a compositionsuitable for supporting and/or building a three-dimensional objects, thecomposition comprising at least one Temperature Sensitive Polymer; andat least one surface-active agent, wherein the composition exhibitsReverse Thermal Gelation (RTG) properties.

[0056] Temperature Sensitive Polymers have been extensively studied overthe last decade. Number of possible molecular mechanisms can cause sharptransitions in these polymeric systems. In most of these mechanismswater is involved.

[0057] The main mechanism of a thermally induced phase separation is therelease of hydrophobically bound water. A locally higher order of watermolecules exists around the hydrophobic unit of the polymer in solution.As gelation occurs the interaction between the hydrophobic units ofpolymer molecules, squeezes out these ordered water molecules into thebulk solution of lower order. This results in an overall disorder orincreased entropy, which is the driving force for hydrophobicassociation.

[0058] One of the most famous groups in Temperature Sensitive Polymersis the Pluronic block copolymers. The Pluronics are a series ofwater-soluble block copolymers, composed of two polyoxyethylene blocksseparated by a polyoxypropylene block. The Pluronics all have thegeneral structure of PEO-PPO-PEO. The ability of Plutonic copolymers toform micelles and gels makes them an important class of surfactants,which find widespread use in industrial applications such as detergency,dispersion stabilization, foaming, emulsification, lubrication andformation of cosmetics and inks, The amphiphilic property of Pluroniccopolymers is the reason for their ability to create micelles above theCMC (critical micellization concentration) and the CMT (criticalmicellization temperature). The micellization of block copolymers, as inthe case of conventional surfactants, obeys the closed associationmodel, which assumes equilibrium between molecularly dispersed copolymer(unimer) and multimolecular aggregates (micelles). In the case ofpluronic, when micellization occurs the degree of structuring of thewater molecules is decreased. The hydrogen bonding structure in thewater is restored and the water entropy increases, overcoming theentropy loss due to the localization of the hydrophobic chains in themicelles. The structure of the pluronic micelles in water has beeninvestigated in many studies. In general, the unimer size is found to beapproximately 1 nm and the micelle size 10 nm, independent of copolymerconcentration.

[0059] In one embodiment, the Temperature Sensitive Polymer is awater-soluble Temperature Sensitive Polymer. In another embodiment, thewater-soluble Temperature Sensitive Polymer is an ABA triblock oligomer,wherein A and B are oligomers. In another embodiment, A is a hydrophilicoligomer and B is a hydrophobic oligomer. In another embodiment, A is ahydrophobic oligomer and B is a hydrophilic oligomer. In anotherembodiment, A and B comprise aliphatic polyether and/or polyester units.In another embodiment, A is poly(ethylene oxide) and B is poly(propyleneoxide).

[0060] Examples of Temperature Sensitive Polymers used with embodimentsof the present invention are:

[0061]

[0062] The water soluble block copolymers of poly(ethyleneoxide)-poly(propylene oxide)-poly(ethylene oxide) which are commerciallyavailable as Poloxamers (ICI company) and Pluronics (Basf company). Thetypes of Pluronic block copolymers which create gels in aqueoussolutions at ambient temperature are: Pluronic: F-127, F-108, F-98,F-88, F-68, F-87, F-77, P-105, P-85, P-75, P-65, P-104, P-94, P-84,L-64, L-63, L-121, L-122.

[0063] In another embodiment, the water-soluble Temperature SensitivePolymer is a multi blocks polymer of (ABA-X)_(m), organized at random orrepetitive configuration, wherein wherein A and B are oligomers, m is aninteger of 1-30, and X is a chain extender. In one embodiment, X isselected from the group consisting of di, tri and poly isocyanates, di,tri and poly carboxylic acids, diacyl halides, triphosgene or anycombination thereof. In another embodiment, A is a hydrophilic oligomerand B is a hydrophobic oligomer. In another embodiment, A is ahydrophobic oligomer and B is a hydrophilic oligomer. In anotherembodiment, the multi block polymer of ABA is a polyurethane, apolycarbonate, a polyester or any combination thereof.

[0064] Polymers synthesized by chain extension of the Pluronic molecule,These polymers has the general structure of poly [Pluronic-X]_(m)Wherein X is a chain extender in the reapiting unit and m is the degreeof polymerizasion (Dp). Examples for chain extenders are: di, tri andpoly isocyanates, di, tri and poly carboxylic acids, di acyl halideslike adipoyl chloride and adipoyl bromides, and triphosgene or anycombination thereof.

[0065] In another embodiment, the Temperature Sensitive Polymer is apoly (N-substituted (meth)acrylamide). In one embodiment, the poly(N-substituted (meth)acrylamide) is a poly (N-isopropyl(meth)acrylamides). In another embodiment, the Temperature SensitivePolymer is a poly vinyl alcohol derivative, hydroxypropylmethylcellulose, ethyl hydroxyethyl cellulose (EHEC) or any combinationthereof.

[0066] Poly (N-substituted acrylamides) like poly N-isopropylacrylamide(Poly NIPAAM) (Eastman Kodak or Aldrich). N-Substituted AAm andMethacrylamide (MAAm) or related monomers, Poly vinyl alcoholderivatives, hydroxypropyl methylcellulose, ethyl hydroxyethyl cellulose(EHEC) (Akzo Nobel) combined with ionic surfactants like SDS.

[0067] Another component of the formulation is a surface-active agent. Asurface-active agent is used to reduce the surface tension of theformulation to the value required for jetting, which is typically around30 dyne/cm. In one embodiment, the surface-active agent for the presentinvention is silicon surface-active agent additive, marketed by BykChemie under the trade name of Byk 345, fluoro-based surface-activeagent or any combination thereof.

[0068] In one embodiment, the support and/or building compositionfurther comprises at least one photo curable reactive component, atleast one photo-initiator, and at least one stabilizer.

[0069] The reactive component is typically chosen to increase thestrength of the temperature responsive gel upon curing. The reactivecomponent gives a hydrophilic cured resin with very weak mechanicalproperties The reactive component polymerizes upon curing at the sametime when the Temperature Sensitive Polymer creates a gel. Thus thecombination of reactive component with the Temperature Sensitive Polymercreates an increase in the strength of the gel due to synergistic effectbetween the Temperature Sensitive Polymer and the reactive curedcomponent. After curing, cooling down the gel below the gelationtemperature, results in liquefying the gel, thus it can easily beremoved by rinsing with water, The reactive component is at least one ofan acrylic component, a molecule having one or more vinyl ethersubstituent, or a water- soluble and/or reducible, that can be dissolvedin the aqueous medium when formulated, and after curing it is capable ofswelling upon exposure to water or to an alkaline or acidic watersolution.

[0070] In one embodiment, the curable reactive component is a(meth)acrylic component. In another embodiment, the (meth)acryliccomponent is a (meth)acrylic monomer, a (meth)acrylic oligomer, or acombination thereof In another embodiment, the (meth)acrylic componentis a polyethylene glycol mono or di (meth)acrylated, polyethertriacrylate or any combination thereof In another embodiment, thereactive component is a water miscible component that is, afterirradiation or curing, capable of dissolving or swelling upon exposureto water or to an alkaline or acidic water solution. In anotherembodiment, the water miscible component is an acryloyl morpholine,(meth)acrylated urethane oligomer derivative of polyethylene glycol, apartially (meth)acrylated polyol oligomer, an (meth)acrylated oligomerhaving hydrophillic substituents or any combination thereof In anotherembodiment, the hydrophilic substituents are acidic substituents, aminosubstituents, hydroxy substituents or any combination thereof. Inanother embodiment, the (meth)acrylic component is beta-carboxyethylacrylate. In one embodiment, the reactive component is a molecule havingone or more vinyl ether substituents. In another embodiment, the vinylether substituent is hydroxy-butyl vinyl ether.

[0071] The acrylic component is typically an acrylic monomer or acrylicoligomer, and may be any one of the examples defined hereinabove.Non-limiting examples of acrylic components for use in the formulationused with embodiments of the present invention are polyethylene glycolmonoacrylate, marked by Laporte under the trade name Bisomer PEA-6, andpolyethylene glycol diacrylate, marked by Sartomer under the tradenames; SR-610 and SR 344, Etoxylated TMPTA: SR 415, Polyethertriacrylate: CN-435, and the like.

[0072] The reactive componenet of the formulaion can also be a watermiscible component that, after curing, is capable of swelling or evendissociating upon exposure to water or to an alkaline or acidic watersolution. Examples of water miscible components used with embodiments ofthe present invention are: Acryloyl morpholine marked by UCB under thetrade name of ACMO, an acrylated urethane oligomer derivative ofpolyethylene glycol-polyethylene glycol urethane diacrylate, a partiallyacrylated polyol oligomer, an acrylated oligomer having hydrophilicsubstituent, or any combination thereof.

[0073] The hydrophilic substituent are acidic substituent, aminosubstituent, hydroxy substituent, or any combination thereof An exampleof an acrylated oligomer with hydrophilic substituent isbeta-carboxyethyl acrylate, which contains cidic substituents. Thereactive component can also be a molecule having one or more vinyl ethersubstituent, which may be any of the compounds as defined hereinabove.An example of vinyl ether for the support and/or building compositionmaterial is hydroxy-butyl vinyl ether, marked by BASF under the tradename of HBVE.

[0074] In one embodiment, the photo-initiator is a free radicalphoto-initiator, a cationic photo-initiator, or any combination thereof.

[0075] In one embodiment, the free radical photo-initiators arebenzophenonies, acylphosphine oxide, alpha-amino ketone or anycombination thereof.

[0076] In one embodiment the photo-initiator further comprises aco-initiator component. In another embodiment the co-initiator componentis triethanol amine.

[0077] The free radical photo-initiator can be any compound thatproduces a free radical on exposure to radiation such as ultraviolet orvisible radiation and thereby initiates a polymerization reaction.Non-limiting examples of some suitable photo-initiators includebenzophenones (aromatic ketones) such as benzophenone, methylbenzophenone, Michlers ketone and xanthones; acylphosphine oxide typephoto-initiators such as 2,4,6-trimethylbenzolydiphenyl phosphine oxide(TMPO), 2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide (TEPO), andbisacylphosphine oxides (BAPO's) benzoins and benzoin alkyl ethers suchas benzoin, benzoin methyl ether and benzoin isopropyl ether and thelike. Non-limiting examples of photo-initiators are alpha- amino ketone,marked by Ciba Specialties Chemicals Inc. (Ciba) under the trade name ofIrgacure 907, and bisacylphosphine oxide (BAPO's), marked by Ciba underthe trade name of I-819.

[0078] The free-radical photo-initiator can be used alone or incombination with a co-initiator. Co-initiators are used with initiatorsthat need a second molecule to produce a radical that is active in theUV-system.

[0079] In one embodiment, the cationic photo-initiator is selected fromthe group comprising: aryldiazonium salts, diaryliodonium salts,triarylsulphonium salts, triarylselenonium salts and triarylsolfoniumhexafluoroantimonate salts, or any combination thereof.

[0080] Suitable cationic photo-initiator used with embodiments of thepresent invention include, for example, compounds which form aproticacids or bronsted acids upon exposure to ultraviolet and/or visiblelight sufficient to initiate polymerization. The photo-initiator usedmay be a single compound, a mixture of two or more active compounds, ora combination of two or more different compounds, i.e. Co-initiators.Non-limiting examples of suitable cationic photo-initiators arearyldiazonium salts, diaryliodonium salts, triarylsulphonium salts,triarylselenonium salts and the like. In one embodiment, the cationicphoto-initiator is a mixture of triarylsolfonium hexafluoroantimonatesalts marketed by Union Carbide as UVI6974.

[0081] Other components of the composition are inhibitors (thermalstabilizers). In one embodiment, the stabilizer is 4-methoxy phenol.Inhibitors are employed in the formulations to permit the use of theformulation at room temperature and elevated temperatures, withoutcausing thermal polymerization.

[0082] Non-limiting examples of characteristic components of thepolymeric compositions are provided in Table 1 herein below. Examples ofpossible formulations of the support and/or building compositions areprovided in Table 2 herein below. TABLE 1 Examples of CharacteristicComponents of the Support and/or Building Compositions # Trade NameChemical Type Function Supplier A Pluronic: PEO—PPO—PEO Temperature BASFF-127, F-108, F-98, F-88, block sensitive F-68, F-87, F-77, P-105,copolymer polymer P-85, P-75, P-65, P-104, P-94, P-84, L-64, L-63,L-121, L-122 B Poly[Pluronic-X]_(m) Polyurethanes, Temperature Home madeChain extension products Polycarconates, sensitive of Pluronic withX-chain polyesters polymer extender. C NIPAAM N-Isopropyl TemperatureAldrich Acryl Amide sensitive polymer D EHEC Ethyl Hydroxy TemperatureAkzo Nobel ethyl cellullose sensitive polymer E Water Water Aqueousmedia F SDS Sodium dodecyl Surface active Aldrich sulphonate agent GBisomer PEA-6 Polyethylene Photo-curable Laport Glycol reactivemonoacrylate monomer Water soluble H SR-344 Polyethylene Photo-curableSartomer Glycol (400) di- reactive acrylate monomer Water soluble I ACMOAcryloyl Photo-curable UCB morpholine reactive monomer Water soluble JHBVE Hydroxy Butyl Vinyl ether BASF Vinyl Ether monomer K Irgacure-2959Alpha-Hydroxy Free radical CIBA ketone photo-initiator For waterbornType I formulations L Triethanol Amine Ternary Amine Free radical J.T.Baker Coinitiator for type II photoinitiator M Byk 345 Silicon SurfaceSurface agent Byk Chemie Additive N MEHQ 4-Methoxy Inhibitor Sigmaphenol (thermal stabilizers)

[0083] TABLE 2 Examples of Possible Formulations of the Support and/orBuilding Compositions Ex- am- ple A B C D E F G H I J K L M N 1 X X X 2X X X 3 X X X X X 4 X X X X 5 X X X X X X 6 X X X X X X 7 X X X X X X 8X X X X X X 9 X X X X X X 10 X X X X X X 11 X X X X X X 12 X X X X X X X13 X X X X X X X

[0084] In one embodiment, the formulation of the support and/or buildingcomposition is presented in entry No. 2.

[0085] In one embodiment, the formulation of the support and/or buildingcomposition is presented in entry No. 1.

[0086] In one embodiment, the formulation of the support and/or buildingcomposition is presented in entry No. 6.

[0087] In one embodiment, the formulation of the support and/or buildingcomposition is presented in entry No. 5.

[0088] Model Composition

[0089] In one embodiment the model composition is used for the buildinga three dimensional object.

[0090] The model composition is formulated to give, after curing, asolid material with mechanical properties that permit the building andhandling of three-dimensional models. The model composition used with anembodiment of the present invention comprises:

[0091] at least one reactive component;

[0092] at least one photo-initiator;

[0093] at least one surface-active agent; and

[0094] at least one stabilizer.

[0095] In one embodiment the reactive component is an acrylic component,a molecule having one or more epoxy substituents, a molecule having oneor more vinyl ether substituents, vinylpyrolidone, vinylcaprolactam, orany combination thereof The acrylic component is an acrylic monomer, anacrylic oligomer, an acrylic crosslinker, or any combination thereof.

[0096] An acrylic monomer is a monofunctional acrylated molecule whichcan be, for example, esters of acrylic acid and methacrylic acid. Anexample of an acrylic monomer used with an embodiment of the presentinvention is phenoxyethyl acrylate, marketed by Sartomer under the tradename SR-339. Another non-limiting example of an acrylic monomer ismarketed by Sartomer under trade name SR-9003.

[0097] An acrylic oligomer is a polyfunctional acrylated molecule whichcan be for example polyesters of acrylic acid and mnethacrylic acid anda polyhydric alcohol, such as polyacrylates and polymethacrylates oftrimethylolpropane, pentaerytiritol, ethylene glycol, propylene glycoland the like. Non-limiting examples of acrylic oligomers are the classesof urethane acrylates and urethane mnethacrylates. Urethane-acrylatesare manufactured from aliphatic or cycloaliphatic diisocyanates orpolyisocyanates and hydroxyl-containing acrylic acid esters. Anon-limiting example is a urethane-acrylate oligomer marketed by Cognisunder the trade name Photomer6010.

[0098] An acrylic crosslinker is a molecule which provides enhancedcrosslinking. Examples of such resins are 1,4-butanediol diacrylate,1,4-butanediol dimethacrylate, 1 ,6-hexamethylene glycol diacrylate,neopentyl glycol dimethacrylate, trimethylol propane trimethacrylate,pentaerythritol triacrylate, penta-erythritol trimethacrylatetriethylene glycol triacrylate, triethylene glycol trimnethacrylate, andthe like. A non-limiting example of an acrylic crosslinker used with oneembodiment of the is trimethylol propane triacrylate, marketed bySartomer under the trade name SR-351. Another non-limiting example of acrosslinker is UVM-45, marketed by CRODA.

[0099] The reactive component in the model composition can also be amolecule having one or more vinyl ether substituents. Conventional vinylether monomers and oligomers which have at least vinyl ether group aresuitable. Non-limiting examples of vinyl ethers are ethyl vinyl ether,propyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether,2-ethylhexyl vinyl ether, butyl vinyl ether, ethyleneglocol monovinylether, diethyleneglycol divinyl ether, butane diol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol monovinyl ether and the like.In one embodiment, the vinyl ether is 1,4 cyclohexane dimethanol divinylether, marketed by ISP under the trade name CHVE.

[0100] The reactive component in the model composition can also be amolecule having one or more epoxy substituents. In one embodiment, theconventional epoxy monomers and oligomers have at least one oxiranemoiety. Non-limiting examples of suitable epoxy containing molecules aredisplayed in Table 3 below: TABLE 3 Examples of Epoxy-ContainingReactive Component Trade Name Type of Material Supplier ERL-4299 or UVR-Bis-(3,4 cyclohexylmethyl) Union Carbide 6128 adipate UVR-6105 and 3,4-Union Carbide UVR-6110 epoxy cyclohexylmethyl-3,4- epoxycyclohexylcarboxylate D.E.R 732 Aliphatic epoxy, Polyglycol Dow chemicalsdiglycidyl ether Vinylcyclohexene 1,2 epoxy-4-vinylcyclohexane UnionCarbide Monoxide D.E.N. 431 Epoxy novolac resin Dow corning UVR-62161,2-epoxy hexadecane Union Carbide UVI-6100 Cycloaliphatic epoxidediluent Union Carbide Vikoflex 7170 FullyI epoxidized soy bean oil ElfAtochem, INC. ERL-4221D 3,4-epoxy cyclohexylmethyl Union Carbide3,4-epoxy cyclohexane carboxylate

[0101] The reactive component of the model composition can comprise anycombination of an acrylic component as defined hereinabove, a moleculehaving one or more epoxy substituents as defined hereinabove, a moleculehaving one or more vinyl ether substituents as defined hereinabove,vinylcaprolactam and vinylpyrolidone.

[0102] In one embodiment, the reactive component of the modelcomposition comprises an acrylic monomer, an acrylic oligomer, anacrylic crosslinker and vinylcaprolactam In another embodiment, thereactive component comprises an acrylic component as defined hereinaboveand a molecule having one or more epoxy substituents as definedhereinabove. In another embodiment, the reactive component of the modelcomposition comprises an acrylic component as defined hereinabove and amolecule having one or more vinyl ether substituents as definedhereinabove. In another embodiment, the reactive component in the modelcomposition comprises a molecule having one or more vinyl ethersubstituents as defined hereinabove, and a molecule having one or moreepoxy substituents as defined hereinabove.

[0103] The photo-initiator of the model composition and of the supportand/or building composition may be the same or different, and is a freeradical photo-initiator, a cationic photo-initiator, or any combinationthereof

[0104] The free radical photo-initiator can be any compound thatproduces a free radical on exposure to radiation such as ultraviolet orvisible radiation and thereby initiates a polymerization reaction.Examples of some suitable photo-initiators include benzophenones(aromatic ketones) such as benzophenone, methyl benzophenone, Michler'sketone and xanthones; acylphosphine oxide type photo-initiators such as2,4,6-trimethylbenzolydiphenyl phosphine oxide (TMPO),2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide (TEPO), andbisacylphosphine oxides (BAPO's); benzoins and bezoin alkyl ethers suchas benzoin, benzoin methyl ether and benzoin isopropyl ether and thelike. Non-limiting examples of photo-initiators are alpha-amino ketone,marketed by Ciba Specialties Chemicals Inc. (Ciba) under the trade nameIrgacure 907, and bisacylphosphine oxide (BAPO's), marketed by Cibaunder the trade name I-8 19.

[0105] The free-radical photo-initiator can be used alone or incombination with a co-initiator. Co-initiators are used with initiatorsthat need a second molecule to produce a radical that is active in theUV-systems. Benzophenone is an example of a photo-initiator thatrequires a second molecule, such as an amine, to produce a reactiveradical After absorbing radiation, benzophenone reacts with a ternaryamine by hydrogen abstraction, to generate an alpha-amino radical whichinitiates polymerization of acrylates. A non-limiting example of a classof co-initiators are alkanolamines such as trimethylamine,methyldiethanolamine and triethanolamine.

[0106] Suitable cationic photo-initiators used with embodiments of thepresent invention include compounds, which form aprotic acids orBronstead acids upon exposure to ultraviolet and/or visible lightsufficient to initiate polymerization, The photo-initiator used may be asingle compound, a mixture of two or more active compounds, or acombination of two or more different compounds, i.e. co-initiators.Non-limiting examples of suitable cationic photo-initiators arearyldiazonium salts, diaryliodonium salts, triarylsulphonium salts,triarylselenonium salts and the like. In one embodiment, the cationicphoto-initiator for the present invention is a mixture oftriarylsolfonium hexafluoroantimonate salts marketed by Union Carbide asUVI-6974.

[0107] Other components of the model composition and the support and/orbuilding composition used with embodiments of the present invention aresurface-active agents and inhibitors (thermal stabilizers). Asurface-active agent is used to reduce the surface tension of theformulation to the value required for jetting, which is typically around30 dyne/cm. In one embodiment of the present invention, a surface-activeagent is silicone surface additive, marketed by Byk Chemie under thetrade name Byk 307. Inhibitors are employed in the formulations of themodel composition and the support and/or building composition to permitthe use of the formulation at high temperature, preferably around 85 C.,without causing thermal polymerization.

[0108] In one embodiment of the present invention, the model compositionfurther comprises at least one pigment and at least one dispersant. Thepigment is a white pigment, an organic pigment, an inorganic pigment, ametal pigment or a combination thereof. In another embodiment of thepresent invention, a white pigment is organic treated titanium dioxide,marketed by Kemira Pigments under the trade name UV TITAN M160 VEG. Anon-limiting example of an organic pigment used with embodiment of thepresent invention is an organic pigment marketed by ElementisSpecialities under the trade name Tint Aid PC 9703. Non-limitingexamples of dispersants used with embodiments of the present inventionare dispersants comprising a copolymer with acidic groups marketed byByk Chemie under the trade name Disperbyk 110, and a dispersantcomprising a high molecular weight block copolymer with pigment affinicgroups, marketed by Byk Chemie under the trade name Disperbyk 163.

[0109] Furthermore, in one embodiment of the present invention,combinations of white pigments and dyes are used to prepare coloredresins. In such combinations, the white pigment has a double task: 1) toimpart opacity; and 2) to shield the dye from UV radiation, to preventbleaching of the resin. Thus, in accordance with one embodiment of thepresent invention, the model composition further comprises a dye. Thedye is chosen so as not to interfere with the curing efficiency of theformulation of the model composition. The dye may be any of a broadclass of solvent soluble dyes. Some non-limiting examples are azo dyes,which are yellow, orange, brown and red; anthraquinone andtriarylmethane dyes which are green and blue; and azine dye which isblack. In one embodiment of the present invention, the dye is SolventRed 127, marketed by Spectra Colors Corp. under the trade nameSpectrasol RED BLG.

[0110] The relative proportions of the different components of the modelcomposition can vary. In one embodiment, the model composition comprisesthe following components: 50% acrylic oligonmer(s), 30% acrylicmonomer(s), 15% acrylic crosslinker, 2% photoinitiator, surface activeagent, pigments, dispersants; and stabilizers.

[0111] Non-limiting examples of formulations of the model compositionare provided hereinbelow in Tables 4-6, to which reference is now made.Tables 4 and 5 illustrate examples of possible formulations of the modelcomposition. Table 6 illustrates examples of colored formulations, whichcomprise pigments, dispersants and dyes, as defined hereinabove. To anyof the examples in Tables 4 and 5 may be added the combination of thecolorants of Table 6. TABLE 4 Examples of Characteristic FormulationComponents of Model Composition Function in the # Trade Name ChemicalType formulation Supplier A Photomer- Urethane Acrylate Oligomer Cognis6010 Oligomer B SR-339 Phenoxy ethyl monomer Sartomer Acrylate C SR-351Trimethylol Cross-linker Sartomer propane triacrylate D Irgacurealpha-Amino Ketone Free radical Ciba 907 photo-initiator SpecialtiesChemical Inc. E BP Benzophenone Free radical Satomer photo-initiator FTriethanol 1. Ternary Amine Free radical Sigma Amine Coinitiator G Byk307 Silicone Surface Surface agent Byk Additive Chemie H MEHQ 4-Methoxyphenol Inhibitor Sigma I Cyracure 3,4 Epoxy- Epoxy Union UVR-6110cyclohexylmethyl-3,4- oligomer Carbide epoxy- cyclohexylcarboxylate JUVI-6974 Mixed Cationic Union Triarylsulfonium photo-initiator CarbideHexafluoroantimonate Salts K CHVE 1,4-cyclohexane Vinyl Ether ISPdimethanol divinyl Monomer ether L UV TITAN Organic Treated Whitepigment KEMIRA M160 VEG Titanium Dioxide PIGMENTS M Disperbyk Copolimerwith acidic Pigment Byk 110 groups Dispersant Chemie N SpectrasolSolvent Red 127 Dye Spectra RED BLG Colors Corp. O Tint Aid Organicpigment Organic Elementis PC 9703 pigment Specialties P Disperbyk Highmolecular weight Pigment Byk 163 block copolymer with Dispersant Chemiepigment affinic groups Q V-Cap Vinylcaprolactam Monomer ISP R V-PyrolVinylpyrolidone Monomer ISP

[0112] TABLE 5 Examples of Possible Formulation Compositions of ModelComposition Example A B C D E F G H I J K Q R 1 X X X X X X 2 X X X X X3 X X X X X 4 X X X X X 5 X X X X X X X 6 X X X X X X 7 X X X X X X 8 XX X X X X 9 X X X X X X 10 X X X X X X X 11 X X X X X 12 X X X X X X X13 X X X X X X X X X X X 14 X X X X X X X 15 X X X X X X X

[0113] TABLE 6 Examples of Colored Formulations of Model CompositionExample L M N 0 P 16 X X 17 X X X 18 X X X X 19 X X 20 X X X

[0114] In one embodiment, the formulation of the model composition ispresented in entry No. 14 of Table No. 5. According to this embodimentthe model composition comprises

[0115] an acrylic oligomer, which can be any acrylic oligomer as definedhereinabove, and which is according to one embodiment a urethaneacrylate oligomer;

[0116] an acrylic monomer, which can be any acrylic monomer as definedhereinabove, and which is according to one embodiment a phenoxy ethylacrylate;

[0117] an acrylic crosslinker, which can be any acrylic crosslinker asdefined hereinabove, and which is according to one embodiment a methylolpropane triacrylate;

[0118] a radical photo-initiator, which can be any radicalphoto-initiator as defined hereinabove, and which is according to oneembodiment an alpha-amino ketone;

[0119] a surface agent, which is according to one embodiment a siliconsurface additive;

[0120] an inhibitor, which is according to one embodiment a4-methoxyphenol; and vinylactam.

[0121] Reference is made to FIG. 1: a typical RTG graph ofviscosity—temperature relation is shown. At a specific temperatureT=T_(min) the specific composition has its minimal viscosity n_(min).Amine Raising the temperature induces an increase in viscosity until atT=T_(gel) the composition is transformed into gel, i.e. an abrupt changein the mechanical properties of the composition occurs. Further raisingthe temperature to T=T₂ increases the viscosity of the gel until therequired viscosity for the supporting and/or building composition isattained. Moreover, the gelation process is reversible, i.e. loweringthe temperature of the gel below T=T_(gel), for example T=T₁, causes thegel to liquefy to its starting liquid phase.

[0122] Furthermore, the polymeric composition has a first low viscosity,n₁, at a first temperatures T₁ that is lower than T_(gel). n₁ iscompatible with inkjet printer at T₁. After being dispensed, thecomposition temperature is typically raised to a temperature aboveT_(gel) whereas the material becomes a stiff gel. At its gel positionthe material typically has favorable characteristics as a support and/orbuilding material. The gel layers typically have the appropriatetoughness and dimensional stability. Furthermore, after the constructionprocess is completed, the gel can easily be washed away by lowering thetemperature below the gelling temperature (T_(gel)) at which temperaturethe gel typically liquefies, followed by rinsing with water. Thecomposition is typically totally water-soluble even at its gel position.In addition, the composition typically has no toxic effect onenvironment and can be disposed without causing any ecological harmfuleffects.

[0123] Embodiments of the present invention relate to using thephenomenon of Reverse Thermal Gelation (RTG) and the materialsexhibiting these characteristics as support materials (SM) in the RP, RTor RM processes. Several basic compositions exhibiting the RTGphenomenon are disclosed; others may be used with embodiments of thepresent invention.

[0124] “Reverse Thermal Gelation” (RTG) is the phenomena whereby amaterial or a solution of a material spontaneously increases inviscosity, and in many instances transforms into a semisolid gel, as thetemperature of the solution is increased above the gelation temperatureof the copolymer. When cooled below the gelation temperature, the gelspontaneously reverses to reform the lower viscosity solution. Thiscycling between the solution and the gel may be repeated because thesol/gel transition does not involve any change in the chemicalcomposition of the polymer system. All interactions to create the gelare physical in nature and do not involve the formation or breaking ofcovalent bonds. “Gelation temperature” means the temperature at which asolution transitions to become a gel. “Aqueous solution” means a waterbased solution having a gel forming block copolymer dissolved therein ata functional concentration, and maintained at a temperature above orbelow the gelation temperature such that gel formation does not occur.

[0125] In the above description, various aspects of the presentinvention have been described. For purposes of explanation, specificconfigurations and details were set forth in order to provide a thoroughunderstanding of the embodiments of the present invention. However, itwill also be apparent to one skilled in the art that the embodiments ofthe present invention may be practiced without the specific detailspresented herein. Furthermore, well-known features may be omitted orsimplified in order not to obscure the embodiments of the presentinvention.

[0126] It will be appreciated by persons skilled in the art that theembodiments of the present invention is not limited by what has beenparticularly shown and described hereinabove, and that numerousmodifications, all of which fall within the scope of the embodiments ofthe present invention, exist. Rather the scope of the invention isdefined by the claim that follows:

What is claimed is:
 1. A composition suitable for supporting and/orbuilding a three-dimensional object, said composition comprising: atleast one Temperature Sensitive Polymer; and at least one surface-activeagent, wherein said composition exhibits Reverse Thermal Gelation (RTG)properties.
 2. The composition according to claim 1, wherein saidTemperature Sensitive Polymer is a water-soluble Temperature SensitivePolymer.
 3. The composition according to claim 2, wherein saidwater-soluble Temperature Sensitive Polymer is an ABA triblock oligomer,wherein A and B are oligomers.
 4. The composition according to claim 3,wherein A is a hydrophilic oligomer and B is a hydrophobic oligomer. 5.The composition according to claim 3, wherein A is a hydrophobicoligomer and B is a hydrophilic oligomer.
 6. The composition accordingto claim 3, wherein A and B comprise aliphatic polyether and/orpolyester units.
 7. The composition according to claim 3, wherein A ispoly(ethylene oxide) and B is poly(propylene oxide).
 8. The compositionaccording to claim 2, wherein said water-soluble Temperature SensitivePolymer is a multi blocks polymer of (ABA-X)_(m), organized at random orrepetitive configuration, wherein A and B are oligomers, m is an integerof 1-30, and X is a chain extender.
 9. The composition according toclaim 8, wherein said X is selected from the group consisting of di, triand poly isocyanates, di, tri and poly carboxylic acids, diacyl halides,triphosgene or any combination thereof.
 10. The composition according toclaim 8, wherein A is a hydrophilic oligomer and B is a hydrophobicoligomer.
 11. The composition according to claim 8, wherein A is ahydrophobic oligomer and B is a hydrophilic oligomer.
 12. Thecomposition according to claim 8, wherein said multi block polymer ofABA is a polyurethane, a polycarbonate, a polyester or any combinationthereof.
 13. The composition according to claim 2, wherein saidTemperature Sensitive Polymer is a poly (N-substituted(meth)acrylamide).
 14. The composition according to claim 13, whereinsaid poly (N4-substituted (meth)acrylamide) is a poly (N-isopropyl(meth)acrylamides).
 15. The composition according to claim 2, whereinsaid Temperature Sensitive Polymer is a poly vinyl alcohol derivative,hydroxypropyl methylcellulose, ethyl hydroxyethyl cellulose (EHEC) orany combination thereof.
 16. The composition according to claim 1,wherein said surface-active agent is capable of reducing the surfacetension of said composition to about 30 dyne/cm.
 17. The compositionaccording to claim 1, wherein said surface-active agent is a siliconsurface-active agent additive, a fluoro-based surface-active agent or acombination thereof.
 18. The composition according to claim 1, whereinsaid composition further comprises: at least one photo curable reactivecomponent; at least one photo-initiator; and at least one stabilizer.19. The composition according to claim 18, wherein said photo curablereactive component is a (meth)acrylic component.
 20. The compositionaccording to claim 19, wherein said (meth)acrylic component is a(meth)acrylic monomer, a (meth)acrylic oligomer, or a combinationthereof.
 21. The composition according to claim 19, wherein said(meth)acrylic component is a polyethylene glycol mono or di(meth)acrylated, polyether triacrylate or any combination thereof. 22.The composition according to claim 18, wherein said reactive componentis a water miscible component that is, after irradiation or curing,capable of dissolving or swelling upon exposure to water or to analkaline or acidic water solution.
 23. The composition according toclaim 22, wherein said water miscible component is an acryloylmorpholine, a (meth)acrylated urethane oligomer derivative ofpolyethylene glycol, a partially (meth)acrylated polyol oligomer, an(meth)acrylated oligomer having hydrophillic substituents or anycombination thereof.
 24. The composition according to claim 23, whereinsaid hydrophilic substituent is an acidic substituent, an aminosubstituent, a hydroxy substituent, or any combination thereof.
 25. Thecomposition according to claim 19, wherein said (meth)acrylic componentis beta-carboxyethyl acrylate.
 26. The composition according to claim19, wherein said reactive component is a molecule having one or morevinyl ether substituents.
 27. The composition according to claim 26,wherein said vinyl ether substituent is hydroxy-butyl vinyl ether. 28.The composition according to claim IS, wherein said photo-initiator is afree radical photo-initiator, a cationic photo-initiator, or anycombination thereof.
 29. The composition according to claim 28, whereinsaid free radical photo-initiator is benzophenone, an acylphosphineoxide, an alpha-amino ketone or any combination thereof.
 30. Thecomposition according to claim 28, wherein said cationic photo-initiatoris selected from the group consisting of aryldiazonium salts,diaryliodonium salts, triarylsulphonium salts, triarylselenonium saltsand triarylsolfonium hexafluoroantimonate salts.
 31. The compositionaccording to claim 28, wherein said photo-initiator further comprises aco-initiator component.
 32. The composition according to claim 31,wherein said co-initiator component is triethanol amine.
 33. Thecomposition according to claim 18, wherein said stabilizer is 4-methoxyphenol.
 34. A method for building a three-dimensional object by threedimensional printing, said method comprising the steps of: dispensing abuilding composition comprising: at least one Temperature SensitivePolymer, wherein said composition exhibits Reverse Thermal Gelation(RTG) properties; and at least one surface-active agent; and gelatingsaid building composition by increasing temperature to above thegelation temperature of said composition, thereby constructing saidthree dimensional object.
 35. The method according to claim 34, whereinsaid Temperature Sensitive Polymer is a water-soluble TemperatureSensitive Polymer.
 36. The method according to claim 35, wherein saidwater-soluble Temperature Sensitive Polymer is an ABA triblock oligomer,wherein A and B are oligomers.
 37. The method according to claim 36,wherein A is a hydrophilic oligomer and B is a hydrophobic oligomer. 38.The method according to claim 36, wherein A is a hydrophobic oligomerand B is a hydrophilic oligomer.
 39. The method according to claim 36,wherein A and B comprise aliphatic polyether and/or polyester units. 40.The method according to claim 36, wherein A is poly(ethylene oxide) andB is poly(propylene oxide).
 41. The method according to claim 35,wherein said water-soluble Temperature Sensitive Polymer is a multiblock polymer of (ABA-X)_(m), organized at random or repetitiveconfiguration, wherein wherein A and E are oligomers, m is an integer of1-30, and X is a chain extender.
 42. The method according to claim 41,wherein said X is selected from the group consisting of di, tri and polyisocyanates, di, tri and poly carboxylic acids, diacyl halides,triphosgene or any combination thereof.
 43. The method according toclaim 41, wherein A is a hydrophilic oligomer and B is a hydrophobicoligomer.
 44. The method according to claim 41, wherein A is ahydrophobic oligomer and B is a hydrophilic oligomer.
 45. The methodaccording to claim 41, wherein said multi block polymer of ABA is apolyurethane, polycarbonate, polyester or any combination thereof. 46.The method according to claim 35, wherein said Temperature SensitivePolymers are poly (N-substituted (meth)acrylamides).
 47. The methodaccording to claim 46, wherein said poly (N-substituted(meth)acrylamides) is poly N-isopropyl (meth)acrylamides).
 48. Themethod according to claim 35, wherein said Temperature Sensitive Polymeris a poly vinyl alcohol derivative, hydroxypropyl methylcellulos, Ethylhydroxyethyl cellulose (EHEC) or any combination thereof.
 49. The methodaccording to claim 34, wherein said surface-active agent is capable ofreducing the surface tension of said composition to about 30 dyne/cm.50. The method according to claim 34, wherein said surface-active agentis a silicon surface-active agent additive, a fluoro-basedsurface-active agent or a combination thereof.
 51. The method accordingto claim 34, wherein said composition further comprises: at least onephoto curable reactive component; at least one photo-initiator; and atleast one stabilizer, whereby said method further comprises the step ofcuring said building composition, thereby increases the strength of saidbuilding composition.
 52. The method according to claim 51, wherein saidphoto curable reactive component is a (meth)acrylic component.
 53. Themethod according to claim 52, wherein said (meth)acrylic component is a(meth)acrylic monomer, a (meth)acrylic oligomer, or a combinationthereof.
 54. The method according to claim 52, wherein said(meth)acrylic component is a polyethylene glycol mono or di(meth)acrylated, polyether triacrylate or any combination thereof. 55.The method according to claim 51, wherein said reactive component is awater miscible component that is, after irradiation or curing, capableof dissolving or swelling upon exposure to water or to an alkaline oracidic water solution.
 56. The method according to claim 55, whereinsaid water miscible component is an acryloyl morpholine, a(meth)acrylated urethane oligomer derivative of polyethylene glycol, apartially (meth)acrylated polyol oligomer, an (meth)acrylated oligomerhaving hydrophillic substituents, or any combination thereof.
 57. Themethod according to claim 56, wherein said hydrophilic substituent is anacidic substituent, an amino substituent, a hydroxy substituent or anycombination thereof.
 58. The method according to claim 52, wherein said(meth)acrylic component is beta-carboxyethyl actylate.
 59. The methodaccording to claim 52, wherein said reactive component is a moleculehaving one or more vinyl ether substituents.
 60. The method according toclaim 59, wherein said vinyl ether substituent is hydroxy-butyl vinylether.
 61. The method according to claim 51, wherein saidphoto-initiator is a free radical photo-initiator, a cationicphoto-initiator, or any combination thereof.
 62. The compositionaccording to claim 61, wherein said free radical photo-initiator isbenzophenone, an acylphosphine oxide, an alpha-amino ketone or anycombination thereof.
 63. The method according to claim 61, wherein saidcationic photo-initiator is selected from the group consisting ofaryldiazonium salts, diaryliodonium salts, triarylsulphonium salts,triarylselenonium salts, triarylsolfonium hexafluoroantimonate salts.64. The method according to claim 61, wherein said photo-initiatorfurther comprises a co-initiator component.
 65. The method according toclaim 64 wherein said co-initiator component is triethanol amine. 66.The method according to claim 51, wherein said stabilizer is 4-methoxyphenol.
 67. A method for supporting a three-dimensional object duringconstruction, said method comprising the step of: contacting said objectwith a support composition, said support composition comprising: atleast one Temperature Sensitive Polymer, wherein said supportcomposition exhibits Reverse Thermal Gelation (RTG) properties; and atleast one surface-active agent; and gelating said support composition byincreasing temperature to above the gelation temperature of saidcomposition, thereby supporting said three dimensional object.
 68. Themethod according to claim 67, further comprising the step of removingsaid support composition after construction of said object by coolingsaid support composition to a temperature below the gelation temperatureof said composition.
 69. The method according to claim 67, wherein saidconstruction comprises Rapid Prototyping (RP), Rapid Manufacturing (RM)or Rapid Tooling (RT).
 70. The method according to claim 67, whereinsaid construction comprises rapid tooling (RT), wherein said rapidtooling (RT) comprises building a casting mold with said supportcomposition for holding said object; and building said object in saidmold.
 71. The method according to claim 70, further comprising the stepof removing said mold by cooling said support composition to atemperature below the gelation temperature of said composition.
 72. Themethod according to claim 67, wherein said construction comprises RapidManufacturing (RM), wherein said rapid manufacturing (RM) comprisesdirect manufacturing of finished parts.
 73. The method according toclaim 67, wherein said Temperature Sensitive Polymer is a water-solubleTemperature Sensitive Polymer.
 74. The method according to claim 73,wherein said water-soluble Temperature Sensitive Polymer is an ABAtriblocks oligomer, wherein A and B are oligomers.
 75. The methodaccording to claim 74, wherein A is a hydrophilic oligomer and B is ahydrophobic oligomer.
 76. The method according to claim 74, wherein A isa hydrophobic oligomer and B is a hydrophilic oligomer.
 77. The methodaccording to claim 74, wherein A and B comprise aliphatic polyetherand/or polyester units.
 78. The method according to claim 74, wherein Ais poly(ethylene oxide) and B is poly(propylene oxide).
 79. The methodaccording to claim 73, wherein said water-soluble Temperature SensitivePolymer is a multi block polymer of (ABA-X)_(m), organized at random orrepetitive configuration, wherein A and B are oligomers, m is an integerof 1-30, and X is a chain extender.
 80. The method according to claim79, wherein said X is selected from the group consisting of di, tri andpoly isocyanates, di, tri and poly carboxylic acids, diacyl halides,triphosgene or any combination thereof.
 81. The method according toclaim 79, wherein A is a hydrophilic oligomer and B is a hydrophobicoligomer.
 82. The method according to claim 79, wherein A is ahydrophobic oligomer and B is a hydrophilic oligomer.
 83. The methodaccording to claim 79, wherein said multi block polymer of ABA is apolyurethane, polycarbonate, polyester or any combination thereof 84.The method according to claim 73, wherein said Temperature SensitivePolymers are poly (N-substituted (meth)acrylamides).
 85. The methodaccording to claim 79, wherein said poly (N4-substituted(meth)acrylamides) is poly (N-isopropyl (meth)acrylamides).
 86. Themethod according to claim 73, wherein said Temperature Sensitive Polymeris a poly vinyl alcohol derivative, hydroxypropyl methylcellulose, Ethylhydroxyethyl cellulose (EHEC) or any combination thereof.
 87. The methodaccording to claim 67, wherein said surface-active agent is capable ofreducing the surface tension of said composition to about 30 dyne/cm.88. The method according to claim 67, wherein said surface-active agentis a silicon surface-active agent additive, a fluoro-basedsurface-active agent additive, or a combination thereof.
 89. The methodaccording to claim 67, wherein said composition further comprises: atleast one photo curable reactive component; at least onephoto-initiator, and at least one stabilizer, whereby said methodfurther comprises the step of curing said support composition, therebyincreases the strength of said support composition.
 90. The methodaccording to claim 89, wherein said photo curable reactive component isa (meth)acrylic component.
 91. The method according to claim 90, whereinsaid (meth)acrylic component is a (meth)acrylic monomer, a (meth)acrylicoligomer, or a combination thereof.
 92. The method according to claim90, wherein said (meth)acrylic component is a polyethylene glycol monoor di (meth)acrylated, polyether triacrylate or any combination thereof.93. The method according to claim 89, wherein said reactive component isa water miscible component that is, after irradiation or curing, capableof dissolving or swelling upon exposure to water or to an alkaline oracidic water solution.
 94. The method according to claim 93, whereinsaid water miscible component is an acryloyl morpholine, a(meth)acrylated urethane oligomer derivative of polyethylene glycol, apartially (meth)acrylated polyol oligomer, an (meth)acrylated oligomerhaving hydrophillic substituents, or any combination thereof.
 95. Themethod according to claim 94, wherein said hydrophilic substituent is anacidic substituent, amino substituent, hydroxy substituent or anycombination thereof.
 96. The method according to claim 90, wherein said(meth)acrylic component is beta-carboxyethyl acrylate.
 97. The methodaccording to claim 89, wherein said reactive component is a moleculehaving one or more vinyl ether substituents.
 98. The method according toclaim 97, wherein said vinyl ether substituent is hydroxy-butyl vinylether.
 99. The method according to claim 89, wherein saidphoto-initiator is a free radical photo-initiator, a cationicphoto-initiator, or any combination thereof.
 100. The compositionaccording to claim 99, wherein said free radical photo-initiator is abenzophenone, an acylphosphine oxide, an alpha-amino ketone or anycombination thereof.
 101. The method according to claim 99, wherein saidcationic photo-initiator is selected from the group consisting ofaryldiazonium salts, diaryliodonium salts, triarylsulphonium salts,triarylselenonium salts, triarylsolfonium hexafluoroantimonate salts.102. The method according to claim 99, wherein said photo-initiatorfurther comprises a co-initiator component.
 103. The method according toclaim 102 wherein said co-initiator component is triethanol amine. 104.The method according to claim 89, wherein said stabilizer is 4-methoxyphenol.
 105. A method for the preparation of a three-dimensional objectby three-dimensional printing comprising the step of: dispensing a modelcomposition from a first dispenser, said model composition comprising:at least one reactive component; at least one photo-initiator; at leastone surface-active agent; and at least one stabilizer, dispensing asupport composition from a second dispenser, said support compositioncomprising: at least one Temperature Sensitive Polymer; at least onesurface-active agent; and combining said model composition and saidsupport composition in predetermined proportions to produce amultiplicity of construction layers for forming said three-dimensionalobject; whereby said model composition is cured resulting in a solidform, and whereby said support composition is gelated by increasingtemperature to above the gelation temperature of said composition,thereby resulting in a gel form.
 106. The method according to claim 105,wherein said preparation of a three- dimensional object furthercomprising the step of removing said support composition afterconstruction of said object by cooling said support composition to atemperature below the gelation temperature of said composition.
 107. Themethod according to claim 105, wherein said reactive component of saidmodel composition is selected from the group consisting of an acryliccomponent, a molecule having one or more epoxy substituents, a moleculehaving one or more vinyl ether substituents, vinylpyrolidone,vinylcaprolactam, or any combination thereof.
 108. The method accordingto claim 105, wherein said reactive component of said model compositionis comprised of at least one acrylic component.
 109. The methodaccording to claim 108, wherein said acrylic component is an acrylicmonomer, an acrylic oligomer, an acrylic crosslinker, or any combinationthereof.
 110. The method according to claim 108, wherein said reactivecomponent of said model composition further comprises a molecule havingone or more epoxy substituents, a molecule having one or more vinylether substituents, vinylcaprolactam, vinylpyrolidone, or anycombination thereof.
 111. The method according to claim 108, whereinsaid reactive component of said model composition further comprisesvinylcaprolactam.
 112. The method according to claim 108, wherein saidreactive component of said model composition is a molecule having one ormore vinyl ether substituents.
 113. The method according to claim 105,wherein said reactive component of said model composition is a moleculehaving one or more epoxy substituents.
 114. The method according toclaim 105, wherein said photo-initiator of said model composition is afree radical photo-initiator, a cationic photo-initiator or anycombination thereof.
 115. The method according to claim 105, whereinsaid model composition further comprises at least one pigment and atleast one dispersant.
 116. The method according to claim 105, whereinsaid pigment is a white pigment, an organic pigment, an inorganicpigment, a metal pigment or a combination thereof.
 117. The methodaccording to claim 105, wherein said model composition further comprisesa dye.
 118. The method according to claim 105, wherein said TemperatureSensitive Polymer is a water-soluble Temperature Sensitive Polymer. 119.The method according to claim 118, wherein said water-solubleTemperature Sensitive Polymer is an ABA triblocks oligomer, wherein Aand B are oligomers.
 120. The method according to claim 119, wherein Ais a hydrophilic oligomer and B is a hydrophobic oligomer.
 121. Themethod according to claim 119, wherein A is a hydrophobic oligomer and Bis a hydrophilic oligomer.
 122. The method according to claim 119,wherein A and B comprise aliphatic polyether and/or polyester units.123. The method according to claim 1 19, wherein A is poly(ethyleneoxide) and B is poly(propylene oxide).
 124. The method according toclaim 118, wherein said water-soluble Temperature Sensitive Polymer is amulti block polymer of (ABA-X)_(m), organized at random or repetitiveconfiguration, wherein A and B are oligomers, m is an integer of 1-30,and X is a chain extender.
 125. The method according to claim 124,wherein said X is selected from the group consisting of di, tri and polyisocyanates, di, tri and poly carboxylic acids, diacyl halides,triphosgene, or any combination thereof.
 126. The method according toclaim 124, wherein A is a hydrophilic oligomer and B is a hydrophobicoligomer.
 127. The method according to claim 124, wherein A is ahydrophobic oligomer and B is a hydrophilic oligomer.
 128. The methodaccording to claim 124, wherein said multi block polymer of ABA is apolyurethane, polycarbonate, polyester or any combination thereof. 129.The method according to claim 118, wherein said Temperature SensitivePolymers are poly (N-substituted (meth)acrylamides).
 130. The methodaccording to claim 129, wherein said poly (N-substituted(meth)acrylamides) is poly (N-isopropyl (meth)acrylamides).
 131. Themethod according to claim 118, wherein said Temperature SensitivePolymer is a poly vinyl alcohol derivative, hydroxypropylmethylcellulose, Ethyl hydroxyethyl cellulose (EHEC) or any combinationthereof.
 132. The method according to claim 105, wherein saidsurface-active agent is capable of reducing the surface tension of saidcomposition to about 30 dyne/cm.
 133. The method according to claim 105,wherein said surface-active agent is a silicon surface-active agentadditive, a fluoro-based surface-active agent additive, or a combinationthereof.
 134. The method according to claim 105, wherein said Supportcomposition further comprises: at least one photo curable reactivecomponent; at least one photo-initiator, and at least one stabilizer,whereby said method further comprises the step of curing said supportcomposition, thereby increases the strength of said composition. 135.The method according to claim 134, wherein said photo curable reactivecomponent is a (meth)acrylic component.
 136. The method according toclaim 135, wherein said (meth)acrylic component is a (meth)acrylicmonomer, a (meth)acrylic oligomer, or a combination thereof.
 137. Themethod according to claim 135, wherein said (meth)acrylic component is apolyethylene glycol mono or di (meth)acrylated, polyether triacrylate orany combination thereof.
 138. The method according to claim 134, whereinsaid reactive component is a water miscible component that is, afterirradiation or curing, capable of dissolving or swelling upon exposureto water or to an alkaline or acidic water solution.
 139. The methodaccording to claim 138, wherein said water miscible component is anacryloyl morpholine, a (meth)acrylated urethane oligomer derivative ofpolyethylene glycol, a partially (meth)acrylated polyol oligomer, an(meth)acrylated oligomer having hydrophillic substituents, or anycombination thereof.
 140. The method according to claim 139, whereinsaid hydrophilic substituent is an acidic substituents, aminosubstituent, hydroxy substituent or any combination thereof.
 141. Themethod according to claim 135, wherein said (meth)acrylic component isbeta-carboxyethyl acrylate.
 142. The method according to claim 135,wherein said reactive component is a molecule having one or more vinylether substituents.
 143. The method according to claim 142, wherein saidvinyl ether substituent is hydroxy-butyl vinyl ether
 144. The methodaccording to claim 134, wherein said photo-initiator is a free radicalphoto-initiator, a cationic photo-initiator, or any combination thereof.145. The composition according to claim 144, wherein said free radicalphoto initiator is a benzophenone, an acylphosphine oxide, analpha-amino ketone or any combination thereof.
 146. The method accordingto claim 144, wherein said cationic photo-initiator is selected from thegroupconsisting of aryldiazonium salts, diaryliodonium salts,triarylsulphonium salts, triarylselenonium salts, triarylsolfoniumhexafluoroantimonate salts.
 147. The method according to claim 144,wherein said photo-initiator further comprises a co-initiator component.148. The method according to claim 147 wherein said co-initiatorcomponent is triethanol amine.
 149. The method according to claim 105,wherein said stabilizer is 4-methoxy phenol.
 150. The method accordingto claim 134, wherein said stabilizer is 4-methoxy phenol.
 151. Themethod according to claim 105, further comprising the step of forming amultiplicity of support layers for supporting said object.
 152. A3-dimensional object is prepared by the method according to claim 34.153. A 3-dimensional object is prepared by a method according to claim67.
 154. A 3-dimensional object is prepared by a method according toclaim 105.